SOCCER: All empires crumble from within, usually when prolonged success distorts the leader's vision.Small mistakes multiply, sometimes becoming big ones. Past success is presented as a guarantee of present judgement until the truth of the situation becomes apparent.

Whether he is willing to admit it or not, Alex Ferguson faced that reality on Wednesday night after his Manchester United team had failed to match opponents they would normally be expected to sweep aside. The end of an empire is a compelling sight, particularly when the imperium was designed and constructed by a man of such singular gifts and temperament as Ferguson. For the observer, all sorts of emotions come into play as the process of entropy begins to exert its destructive effect.

Those emotions are as nothing, however, compared with the feelings that will be churning within the United manager's own mind as he looks ahead and recognises that, finally, his days at Old Trafford are numbered.

Called to a meeting with destiny in Lisbon's Estadio Da Luz on a night when the club's glorious past was expected to provide the inspiration for a sort of spiritual rebirth, he proved powerless to alter the course of a match that, while vigorous and entertaining, lacked true quality. United's recent revival in the Premiership was shown to be irrelevant to their hopes of making progress in Europe; on the night, virtually every component of the team was found wanting.

From Benfica to Burton Albion is quite a leap, but it is the one that Ferguson finds himself facing as he searches for a suitable encore with which to close his 20-year reign now that elimination from the Champions League has removed his preferred curtain call. His new target will be to ensure that the closing months of a glorious era do not leave Gary Neville, Ryan Giggs and Paul Scholes without a final trophy to mark the passing of United's golden generation.

In the Premiership his team lie in second place but languish 10 points adrift of Chelsea, with a game in hand. Given Jose Mourinho's success in ensuring that his players have not fallen prey to complacency in the wake of last season's title-winning performance, even a seven-point gap going into the new year would hardly seem to offer much hope. Mourinho's side are made of harder stuff than Kevin Keegan's Newcastle United or even Arsene Wenger's Arsenal, the teams whose double-digit leads were eroded as Ferguson so brilliantly conducted the two most memorable of his eight championship-winning campaigns.

Driven by a man who will certainly not want to leave the scene of his greatest triumphs with head bowed, United are unlikely to give up the chase.

Between now and the end of the season they may well match Chelsea's performance stride for stride, in terms of wins and points. But the core of the side does not seem a firm enough base from which to launch the kind of assault that withered other opponents, not least because - and this was particularly evident in the direct comparison with Benfica - they have fallen below the standards of physical fitness to be found at Europe's leading clubs.

Some of the markers on the path of decline included the bitterness surrounding the departure of David Beckham, whose fame brought out Ferguson's worst instincts; the row with JP McManus and John Magnier over the ownership of a racehorse, making possible Malcolm Glazer's takeover of the club; the inability to persuade Rio Ferdinand to concentrate on justifying a world-record transfer fee for a defender; the decision not only to invite Carlos Queiroz back into the fold but to give him greater powers over training and tactics; and the failure to make adequate provision for the inevitable waning of the powers of midfield enforcer Roy Keane, the team's single most important figure.

By themselves, perhaps only the last would have exerted a significant effect on the club's fortunes. Taken together they form a pattern that has steadily undermined Manchester United's claim to pre-eminence.

None of this should come as any great surprise. Although Ferguson's glittering achievements place him among the handful of English football's greatest managers, the voracity of his appetite for success probably ensured that he would not be the shrewdest judge of the timing of his own departure. His original retirement date, in 2002, looked then like the right time to go; the decision to rescind it was the biggest mistake of the lot. All the errors listed above have been committed in the last three years.

By the start of next season the landscape of English football will look very different. In all likelihood both the national team and the country's most famous club will have new managers. Martin O'Neill is the firm favourite with the bookmakers, and probably with the fans, too, but the Glazers may want an internationally renowned figure.

As Ferguson nears the exit he can look back on achievements he will never see surpassed. It would be unwise, however, to expect him to go quietly.